#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int find(int sz, int arr[])
{
	int sum = 0;
	int i = 0;
	for (i = 0; i < sz; i++)
	{
		sum ^= arr[i];
	}

	return sum;
}

int main()
{
	int arr[] = { 1,2,3,4,5,1,2,3,4 };
	int sz = sizeof(arr) / sizeof(1);
	int ret = find(sz, arr);
	printf("%d", ret);
	return 0;
}